From f5e89b3f47cbe2e7ebacd607bae363044a4b5dac Mon Sep 17 00:00:00 2001
From: Brecht Van Lommel <brechtvanlommel@pandora.be>
Date: Tue, 19 Feb 2008 12:13:35 +0000
Subject: [PATCH] Bugfix: this adds some epsilons (FLT_EPSILON, so quite small)
 to the raytracing intersection code, to avoid rays slipping through between
 triangles, this would mostly show up with sceen aligned quads and baking of
 height maps for example. Epsilon's are not pretty, but I haven't found a
 reliable way around them.

---
 .../blender/render/intern/source/raytrace.c   | 22 ++++++++++---------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/source/blender/render/intern/source/raytrace.c b/source/blender/render/intern/source/raytrace.c
index d18e22c3bfb..7423a11764d 100644
--- a/source/blender/render/intern/source/raytrace.c
+++ b/source/blender/render/intern/source/raytrace.c
@@ -635,6 +635,8 @@ void RE_ray_tree_done(RayTree *tree)
 
 /* ************ raytracer **************** */
 
+#define ISECT_EPSILON ((float)FLT_EPSILON)
+
 /* only for self-intersecting test with current render face (where ray left) */
 static int intersection2(RayFace *face, int ob, RayObjectTransformFunc transformfunc, RayCoordsFunc coordsfunc, void *userdata, float r0, float r1, float r2, float rx1, float ry1, float rz1)
 {
@@ -692,13 +694,13 @@ static int intersection2(RayFace *face, int ob, RayObjectTransformFunc transform
 	if(divdet!=0.0f) {
 		u1= det1/divdet;
 
-		if(u1<=0.0f) {
+		if(u1<ISECT_EPSILON) {
 			det= t00*(m1*r2-m2*r1);
 			det+= t01*(m2*r0-m0*r2);
 			det+= t02*(m0*r1-m1*r0);
 			v= det/divdet;
 
-			if(v<=0.0f && (u1 + v) >= -1.0f) {
+			if(v<ISECT_EPSILON && (u1 + v) > -(1.0f+ISECT_EPSILON)) {
 				return 1;
 			}
 		}
@@ -714,13 +716,13 @@ static int intersection2(RayFace *face, int ob, RayObjectTransformFunc transform
 		if(divdet!=0.0f) {
 			u2= det1/divdet;
 		
-			if(u2<=0.0f) {
+			if(u2<ISECT_EPSILON) {
 				det= t20*(m1*r2-m2*r1);
 				det+= t21*(m2*r0-m0*r2);
 				det+= t22*(m0*r1-m1*r0);
 				v= det/divdet;
 	
-				if(v<=0.0f && (u2 + v) >= -1.0f) {
+				if(v<ISECT_EPSILON && (u2 + v) >= -(1.0f+ISECT_EPSILON)) {
 					return 2;
 				}
 			}
@@ -860,7 +862,7 @@ int RE_ray_face_intersection(Isect *is, RayObjectTransformFunc transformfunc, Ra
 
 		divdet= 1.0f/divdet;
 		u= det1*divdet;
-		if(u<0.0f && u>-1.0f) {
+		if(u<ISECT_EPSILON && u>-(1.0f+ISECT_EPSILON)) {
 			float v, cros0, cros1, cros2;
 			
 			cros0= m1*t02-m2*t01;
@@ -868,11 +870,11 @@ int RE_ray_face_intersection(Isect *is, RayObjectTransformFunc transformfunc, Ra
 			cros2= m0*t01-m1*t00;
 			v= divdet*(cros0*r0 + cros1*r1 + cros2*r2);
 
-			if(v<0.0f && (u + v) > -1.0f) {
+			if(v<ISECT_EPSILON && (u + v) > -(1.0f+ISECT_EPSILON)) {
 				float labda;
 				labda= divdet*(cros0*t10 + cros1*t11 + cros2*t12);
 
-				if(labda>0.0f && labda<1.0f) {
+				if(labda>-ISECT_EPSILON && labda<1.0f+ISECT_EPSILON) {
 					is->labda= labda;
 					is->u= u; is->v= v;
 					ok= 1;
@@ -893,18 +895,18 @@ int RE_ray_face_intersection(Isect *is, RayObjectTransformFunc transformfunc, Ra
 			divdet= 1.0f/divdet;
 			u = det1*divdet;
 			
-			if(u<0.0f && u>-1.0f) {
+			if(u<ISECT_EPSILON && u>-(1.0f+ISECT_EPSILON)) {
 				float v, cros0, cros1, cros2;
 				cros0= m1*t22-m2*t21;
 				cros1= m2*t20-m0*t22;
 				cros2= m0*t21-m1*t20;
 				v= divdet*(cros0*r0 + cros1*r1 + cros2*r2);
 	
-				if(v<0.0f && (u + v) > -1.0f) {
+				if(v<ISECT_EPSILON && (u + v) >-(1.0f+ISECT_EPSILON)) {
 					float labda;
 					labda= divdet*(cros0*t10 + cros1*t11 + cros2*t12);
 					
-					if(labda>0.0f && labda<1.0f) {
+					if(labda>-ISECT_EPSILON && labda<1.0f+ISECT_EPSILON) {
 						ok= 2;
 						is->labda= labda;
 						is->u= u; is->v= v;